Numerical analysis of point-source infrared radiation phenomena of rocket exhaust plumes at low and middle altitudes

Rocket exhaust plume treated as a significant radiation source has been widely used in space-based detection. In this paper, infrared radiation signatures of plumes were studied in the view of the phenomenon. The reacting plume flows were calculated by an axisymmetric computational fluid dynamics (CFD) solver. Radiative properties of gases were evaluated with the statistical narrow-band (SNB) model by relying on the NASA-3080 database. The line-of-sight (LOS) based on the single-line-group (SLG) approximation was employed for radiative transfer computations. The numerical model was validated against reference data. Based on this model, radiation characteristics of Atlas-II liquid rocket plumes were computed and analyzed in aspects of afterburning, atmospheric attenuation, spectral bands and observation angle. Results show that afterburning has a significant improvement in the wavelengths of 1.5-6.0 mu m. Also, the atmospheric attenuation greatly decreases the plume radiance at low altitudes but it can be ignored above 40 km. Radiance is strongly dependent on the spectral bands. The altitude-varying spectral dependency can contribute to the rocket altitude estimation. The effect of the observation angle on the radiance distributions is varying with the spectra band and the flight altitude. These results are helpful for the design of the rocket motors and the application of the infrared detecting system.